This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Objective: To study a new vaccine approach to HIV. Our laboratory has recently made an interesting series of observations that may have important implications for HIV vaccine design. We recently examined the ontogeny of epitope expression on the surface of infected cells. Surprisingly, CD8+ T cells recognized Gag- and Pol-derived epitopes by two hours post-infection, before integration and viral protein synthesis. We have also shown that Nef down-regulates major histocompatibility complex class I (MHC-I) molecules at 12 hrs post-infection, diminishing the efficacy of CD8+ T cells that recognize late-expressed epitopes. Thus, there is only a 12 hr window for CD8+ T cell recognition. Our preliminary data, therefore, suggest that a CD8+ T cell-based HIV vaccine should stimulate responses against proteins whose epitope are present early on the surface of an infected cell. We hypothesize that vaccine-induced CD8+ T cell responses directed against multiple epitopes that are present on the cell surface soon after infection and before Nef-mediated MHC-I down-regulation will control replication of the highly pathogenic SIVmac239 isolate. We will test this hypothesis by using a novel mini-gene vaccination technique to ender multiple responses against proteins whose epitope are present early on the surface of an infected cell. We have examined the ontogeny of epitope on the surface of infected cells for 5 of the 9 viral proteins (Gag, Pol, Env, Tat, and Nef). We have defined CD8+ T cell responses directed against the remaining 4 viral proteins and are testing these cells in our in vitro kinetics assay. Production of the mini-gene vaccine constructs for Gag, Nef, Rev, and Tat is complete and vaccination of animals has begun. This research used WNPRC Animal Services, Genetics Services, and Immunology &Virology Services.